Page 343 - My FlipBook

MANAGEMENT OF CAVITIES BY CLASSES. 205

ring in the pits of the bicuspids. Under equal conditions of sus-
ceptibility and local conditions among the different teeth, decay
in pits and fissures would occur -within about a certain time after
the teeth take their places in the arch. In highly susceptible
persons this will be within from one to three years, and at a
later time as the susceptibility is less. Therefore, while this class
is first to appear in the individual teeth, the cavities are scattered
over a considerable period in the person, and, as both the sus-
ceptibility and local conditions vary greatly in different persons,
we meet with this class of cavities at various ages of persons. It
is only through the careful observation of records of many per-
sons that general rules are made out.
The local conditions relate almost entirely to the form and
depth of pits and fissures. Well-closed pits rarely decay. In
very susceptible persons decay begins early in deep pits and in
fissures. In immune persons, decay may not occur at all in these.
Pit cavities in the second molars begin to occur at from four-
teen to sixteen, and often make rapid progress in highly suscep-
tible persons. If it is remembered that these cavities usually
appear in very susceptible families in from one to three years
after the eruption of the teeth, and the order and time of their
eruption is kept in mind, the whole matter will be materially
simplified and the reasons for the order of their appearance will
be readily grasped. One will therefore look especially after these
teeth at the proper time. The pit cavities are the simplest of all
cavities to treat, and, when taken in time, rarely present any
considerable difficulty. It should be remembered, however, that
in occlusal surfaces, the whole surface of the fillings is fully
exposed to thermal changes by hot and cold drinks and foods.
They are, therefore, in more danger from thermal sensitiveness
in proportion to their area than other cavities. In proximal cav-
ities, much of the area of the fillings is shielded by the proximat-
ing tooth. In buccal cavities the fillings are not so directly exposed
to thermal changes, therefore where dealing with very deep cav-
ities especial care should be had to shield the pulp from thermal
changes. This is best done by covering the pulpal wall with a
layer of oxyphosphate of zinc and making the filling over this,
after it has become fully hard. Theoretically, gutta-percha is
the best non-conductor, but, practically, it is too soft to serve as
the support of a permanent filling and should never be used.
Filling over softened dentin. There is a practice among
many in the profession of leaving a portion of softened dentin
in deep occlusal cavities and filling over it, claiming that when